JP2009141374A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a high quality by having a phosphor layer including a specific phosphor. <P>SOLUTION: This light emitting device 200 has a light emitting element 206 for emitting the light of a wavelength of 410 nm, 360 nm, 470 nm or 405 nm, and the phosphor layer 209 arranged on the light emitting element 206 and including the phosphor 210. The phosphor 210 has a core particle composed of an alkaline earth metal silicate phosphor having the composition represented by formula (1):(M<SB>1-x</SB>E<SB>ux</SB>)<SB>2</SB>Si<SB>y</SB>O<SB>2y+2</SB>(in the formula (1), M is at least one kind of alkaline earth metal element selected from a group composed of Ca, Sr and Ba, x is 0.001 to 0.1, and yis 0.9 to 1.1), and a surface layer material such as a silicone resin arranged on a surface of the core particle. A light emitting spectrum excited by the light of the wavelength has the single light emitting peak between a wavelength 540 nm and 600 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting device such as an LED using a phosphor.

  LED lamps using light emitting diodes are used in various display devices such as portable devices, PC peripheral devices, OA devices, various switches, backlight light sources, and display plates. Since the LED chip is a semiconductor element, it has a long lifetime and high reliability, and when used as a light source, its replacement work is reduced. Therefore, application to various uses has been attempted.

  In the LED lamp as described above, an LED chip that emits long-wavelength ultraviolet light having a wavelength of around 400 nm, for example, an LED chip having a GaN-based compound semiconductor layer is used as a light source. For this reason, the phosphor used for the LED lamp is required to absorb a long wavelength ultraviolet ray as described above and to emit visible light efficiently.

  A known silicate phosphor activated by divalent europium efficiently absorbs long-wavelength ultraviolet light having a wavelength of about 360 to 500 nm and efficiently emits yellow light having a peak wavelength of about 550 nm. It is expected as a yellow phosphor used in lamps and the like.

  In applying the LED lamp to various uses, it has been proposed to increase the service life of the light emitting element (see, for example, Patent Document 1). This document relates to the improvement of the service life as a common technology for oxide, sulfide, aluminate, borate, vanadate and silicate emitters. Coating techniques are described.

Regarding YAG-Ce-based, nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ : Eu, Cr, a method of reducing luminescence variation by performing microencapsulation with an organic coating (for example, Patent Document 2) is disclosed. reference). In addition, YAG phosphors have been developed to improve dispersibility by surface modification (see, for example, Patent Document 3).
JP 2002-223008 A JP 2003-46141 A JP 2003-37295 A

  However, it has been confirmed that a light emitting device such as an LED lamp using a conventional europium activated silicate phosphor is uneven in light emission and the light emission output is reduced when used for a long time. Such a phenomenon becomes a factor of deteriorating the quality of the LED lamp.

  Accordingly, an object of the present invention is to provide a high-quality light-emitting device.

A light emitting device according to an embodiment of the present invention includes a light emitting element that emits light having a wavelength of 410 nm, 360 nm, 470 nm, or 405 nm,
A phosphor layer disposed on the light-emitting element and containing a phosphor;
The phosphor is disposed on the surface of the core particle composed of an alkaline earth metal silicate phosphor having a composition represented by the following general formula (1), and is a silicone resin, epoxy resin, fluororesin, tetraethoxy A surface layer material made of at least one selected from silane, silica, zinc silicate, aluminum silicate, calcium polyphosphate, silicone oil, and silicone grease, and excited by light having a wavelength of 410 nm, 360 nm, 470 nm, or 405 nm The emission spectrum is characterized by having a single emission peak between wavelengths 470 nm to 610 nm.

(M _1-x Eu _x ) ₂ Si _y O _{2y + 2} (1)
(In the general formula (1), M is at least one alkaline earth metal element selected from the group consisting of Ca, Sr and Ba, x is 0.001 or more and 0.1 or less, and y is 0.00. 9 or more and 1.1 or less.)

  According to one embodiment of the present invention, a high-quality light-emitting device is provided.

  Embodiments of the present invention will be described below.

  As a result of intensive studies on the conventional europium activated silicate phosphor, the present inventors have found that this phosphor has hygroscopicity. The europium activated silicate phosphor easily aggregates depending on the environment when stored for a long period of time, resulting in various problems.

  When the particulate phosphor used in the fluorescent layer of the LED lamp aggregates, the output of the LED lamp decreases. In the case where the aggregation of the phosphor occurs when the LED lamp is manufactured, it is not possible to form a phosphor layer in which the phosphor is uniformly dispersed in the resin. As a result, the light emission from the LED lamp becomes uneven, and the light emission output from the LED lamp also decreases.

  In order to improve the quality of light-emitting devices such as LED lamps, the present invention has been made based on the knowledge that it is essential to improve the moisture resistance of the europium-activated silicate phosphor.

  The europium activated silicate phosphor gives an emission spectrum having a first wavelength near 550 nm by selecting the type and composition of the alkaline earth metal element. The spectrum at this time generally has a second wavelength in the vicinity of 500 nm as shown in FIG. With respect to such a second wavelength, for example, G.I. Blasse, W.M. L. Wanmaher, J. et al. W. terVrugt, and A.A. Brill, Philips Res. Repts, 23, 189-200, (1968). (2) S.M. H. M.M. Port, W. Janssen, G.M. Blasse, J. et al. Alloys and Compounds, 260, 93-97, (1997).

  When the second wavelength is present in the emission spectrum, the hygroscopicity of the europium activated silicate phosphor is significantly increased, and by removing this second wavelength, the hygroscopicity of the europium activated silicate phosphor is improved. Has been found by the present inventors. That is, in order to obtain a europium activated silicate phosphor with reduced hygroscopicity, the second wavelength is removed and the emission peak existing between wavelengths of 540 nm and 600 nm is made single as shown in FIG. There must be. Europium activated silicate phosphors having a single emission peak were prepared from core particles made of alkaline earth metal silicate phosphors of a specific composition.

  That is, the phosphor according to the embodiment of the present invention includes a core particle made of an alkaline earth metal silicate phosphor having the composition represented by the general formula (1), and a surface layer material disposed on the surface of the core particle. And have.

  The core particle is activated by divalent europium and can be synthesized by, for example, the following method.

First, a predetermined amount of the constituent element oxide powder is weighed, an appropriate amount of ammonium chloride is added as a crystal growth agent, and mixed with a ball mill or the like. Instead of the oxide powder, various compounds that can be converted into oxides by thermal decomposition can also be used. For example, Eu ₂ O ₃ or the like can be used as the Eu material, CaCO ₃ or the like can be used as the Ca material, SrCO ₃ can be used as the Sr material, and SiO ₂ or the like can be used as the Si material.

  As the crystal growth agent, ammonium other than ammonium chloride, chloride of alkali metal or alkaline earth metal, fluoride, bromide, or iodide may be used. In order to prevent an increase in hygroscopicity, the amount of the crystal growth agent added is desirably about 1.0 wt% or more and 30 wt% or less with respect to the entire raw material powder.

After that, it is placed in a crucible and fired at a temperature of 1000 to 1600 ° C. for 3 to 7 hours in a reducing atmosphere of N ₂ and H ₂ . The obtained fired product is pulverized in water, sieved, and dehydrated by suction filtration. Finally, an alkaline earth metal silicate phosphor activated with divalent europium represented by the general formula (1) can be obtained by drying at 150 ° C. in a dryer.

  In the embodiment of the present invention, since it is necessary to reduce the hygroscopicity of the phosphor, the amount of water contained in the initial core particles is required to be as small as possible. Specifically, it is desirable that the core particles be sufficiently dried so that the water content in the core particles is less than 1 wt%. The water content in the core particles can be measured by Karl Fischer moisture analysis.

  In the general formula (1), M is at least one alkaline earth metal element selected from the group consisting of Ca, Sr and Ba. Since it is necessary to obtain the first wavelength of 540 nm to 600 nm, Sr and Ba are preferably contained as M.

  In the said General formula (1), x has shown the composition ratio of Eu which is an activator, The range is prescribed | regulated to 0.001 or more and 0.1 or less. When x is less than 0.001, the light emission luminance decreases. On the other hand, when x exceeds 0.1, sufficient light emission luminance cannot be obtained by concentration quenching.

  Further, y in the general formula (1) indicates the composition ratio of Si, and the range is set to 0.9 or more and 1.1 or less. When y is less than 0.9, the second wavelength in the vicinity of 500 nm as shown in FIG. 1 is developed, and the hygroscopicity is remarkably increased. On the other hand, if y exceeds 1.1, sufficient light emission luminance cannot be obtained. Preferably, y is in the range of 0.95 to 1.05.

The surface of the core particle as described above is selected from silicone resin, epoxy resin, fluororesin, tetraethoxysilane (TEOS), silica, zinc silicate, aluminum silicate, calcium polyphosphate, silicone oil, and silicone grease. A surface layer material made of at least one of the above is disposed. Zinc silicate and aluminum silicate are represented by, for example, ZnO.aSiO ₂ (1 ≦ a ≦ 4) and Al ₂ O ₃ .bSiO ₂ (1 ≦ b ≦ 10), respectively. The surface of the core particle need not be completely covered with the surface layer material, and a part thereof may be exposed. If the surface layer material made of the material as described above exists on the surface of the core particle, the effect can be obtained.

  The surface layer material can be arranged on the surface of the core particle using the dispersion or solution. After immersing the core particles in the dispersion or solution for a predetermined time, the surface layer material is disposed by drying by heating or the like. In order to obtain the effect of the surface layer material without impairing the original function as the phosphor, the surface layer material is preferably present at a ratio of about 0.1 to 50% of the volume of the core particles.

  FIG. 3 shows a cross section of a light emitting device according to an embodiment of the present invention.

  In the illustrated light emitting device, the resin stem 200 has a lead 201 and a lead 202 formed by molding a lead frame, and a resin portion 203 formed integrally therewith. The resin portion 203 has a concave portion 205 whose upper opening is wider than the bottom portion, and a reflective surface 204 is provided on the side surface of the concave portion.

  A light emitting chip 206 is mounted with Ag paste or the like at the center of the substantially circular bottom surface of the recess 205. As the light-emitting chip 206, a chip that emits ultraviolet light or a chip that emits light in the visible region can be used. For example, it is possible to use a GaAs-based or GaN-based semiconductor light emitting element. The electrodes (not shown) of the light emitting chip 206 are connected to the leads 201 and 202 by bonding wires 207 and 208 made of Au or the like, respectively. The arrangement of the leads 201 and 202 can be changed as appropriate.

  A fluorescent layer 209 is disposed in the recess 205 of the resin portion 203. The fluorescent layer 209 can be formed by dispersing the phosphor 210 according to the embodiment of the present invention in a resin layer 211 made of, for example, a silicone resin at a rate of 5 wt% to 50 wt%.

  As the light emitting chip 206, a flip chip type having an n-type electrode and a p-type electrode on the same surface can be used. In this case, problems caused by the wires such as wire breakage and peeling and light absorption by the wires are solved, and a highly reliable and high-luminance semiconductor light-emitting device can be obtained. In addition, an n-type substrate may be used for the light emitting chip 206 to have the following configuration. Specifically, an n-type electrode is formed on the back surface of the n-type substrate, a p-type electrode is formed on the upper surface of the semiconductor layer on the substrate, and the n-type electrode or the p-type electrode is mounted on a lead. The p-type electrode or the n-type electrode can be connected to the other lead by a wire.

  The size of the light emitting chip 206 and the size and shape of the recess 205 can be changed as appropriate. The phosphor according to the embodiment of the present invention exhibits a blue-green-red emission color when excited with light having a wavelength of 360 nm to 500 nm. When the phosphor according to the embodiment of the present invention is used in combination with a blue light-emitting phosphor and a red light-emitting phosphor, white light can be obtained.

  Since the phosphor according to the embodiment of the present invention is excellent in moisture-proofing power, a high-quality light-emitting device can be obtained with a stable output with no emission unevenness by providing a phosphor layer containing this phosphor.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further in detail, this invention is not limited only to an Example.

  Various phosphors were synthesized and their moisture resistance was examined. The phosphor was housed in a dish having an inner diameter of 20 mm and a depth of 2 mm, and stored in a box controlled at a humidity of 70% and a temperature of 25 ° C. After the elapse of 24 hours, the change in the shape of the phosphor was visually observed, and the moisture content (m) relative to 1 mol of the phosphor was measured by Karl Fischer moisture analysis, and the moisture resistance was evaluated as follows.

A: No change, m <1%
B: Aggregation hardening, 1% ≦ m <3%
C: Swell, m ≧ 3%
In addition, the spectral intensity (Ib) at the first wavelength (λ _max ) and the spectral intensity (Ia) at the second wavelength (λ _max −80) nm are measured to obtain the spectral intensity ratio (Ia / Ib). It was. When the spectral ratio (Ia / Ib) is 0.1 or less, there is substantially no second wavelength. Therefore, when this spectral intensity ratio (Ia / Ib) is 0.1 or less, It is defined as having one emission peak.

  Further, the obtained phosphor was dispersed in a silicone resin to produce a light emitting device as shown in FIG. 3, and the light emission output was measured. The light emission output varies depending on the amount of the phosphor dispersed in the resin, but the output at the amount of the phosphor capable of obtaining the maximum output was defined as the light emitting device output.

Example 1
First, a phosphor having a composition represented by (Sr _0.92 Ba _0.06 Eu _0.02 ) ₂ SiO ₄ to be core particles was prepared. As raw material powders, SrCO ₃ powder, BaCO ₃ powder, Eu ₂ O ₃ powder and SiO ₂ powder were prepared and weighed in predetermined amounts. NH ₄ Cl as a crystal growth agent was added at a ratio of 1.5 wt% with respect to the total amount of the raw material powder, and mixed uniformly by a ball mill.

The obtained mixed raw material was filled in an alumina crucible with a lid and fired at 1000 ° C. for 4 hours in a reducing atmosphere composed of a mixed gas of N ₂ / H ₂ . After cooling to 25 ° C., the fired product was pulverized in water. After passing through the sieve, it was dried in an oven at 150 ° C. for about 10 hours to obtain a phosphor as core particles.

  On the other hand, a silicone resin was prepared as a surface layer material, and this was dissolved in toluene to prepare a solution. The core particles were immersed in this solution for 30 minutes and then dried by a vacuum evaporator to obtain a phosphor having a surface layer material made of a silicone resin on the surface.

  When the moisture resistance was evaluated by the method described above, it was A. The composition of the phosphor is shown in Table 1 below together with the evaluation of moisture resistance.

  The phosphor was combined with an excitation light source of 395 nm to produce the light emitting device of Example 1. The first wavelength was 570 nm and the spectral ratio (Ia / Ib) was 0.07.

  Without providing the surface layer material, the moisture resistance of the core particles used in Example 1 as they were was investigated as the phosphor of Comparative Example 1 in the same manner as described above. The obtained results are shown in Table 2 below together with the composition of the phosphor.

  A light emitting device of Comparative Example 1 was produced in the same manner as in Example 1 except that the phosphor of Comparative Example 1 was used, and the characteristics were evaluated. It was confirmed that the band wavelength and the spectral ratio in the light emitting device of Comparative Example 1 were the same as those of the light emitting device of Example 1. When the output of the light emitting device of Comparative Example 1 was set to 1, the relative light emitting device output was found to be 1.1 in Example 1.

  The characteristics (band wavelength, emission spectrum ratio, light-emitting device output) of the light-emitting devices of Examples and Comparative Examples are shown in Tables 3 and 4 below, respectively.

  Further, various phosphors were synthesized as shown in Tables 1 and 2 below.

  The phosphors of Examples 2 to 10 were prepared by using the same core particles as in Example 1 and changing the material of the surface layer material disposed on the surface thereof. The epoxy resin (Example 2) and the fluororesin (Example 3) were arranged on the surface of the core particles by the same method as described above. TEOS (Example 4) was dissolved in toluene to prepare a solution. After immersing the core particles in this solution for 30 minutes, they were dried by a vacuum evaporator and placed on the surface of the core particles. Also, silicone oil (Example 5) and silicone grease (Example 6) were dissolved in hexane to prepare solutions. After immersing the core particles in this solution for 30 minutes, they were dried by a vacuum evaporator and placed on the surface of the core particles.

  The phosphors of Examples 7 to 10 were produced by arranging the surface layer material on the surface of the core particle by the following method.

(Example 7)
Core particles were dispersed in an aqueous choline solution containing 10 wt% SiO ₂ . This was stored in an evaporating dish and heated to 150 ° C. to evaporate the water to obtain a solid, and further washed with water to place a silica film on the surface of the core particles.

(Example 8)
The core particles were dispersed in a water glass (K ₂ O.3SiO ₂ ) aqueous solution, and the pH was adjusted to 6.0 by adding an Al (NO ₃ ) ₃ aqueous solution. Further, washing with water, suction filtration, drying, and aluminum silicate were arranged on the surface of the core particles.

Example 9
The core particles were dispersed in an aqueous solution of water glass (K ₂ O.3SiO ₂ ), and an aqueous ZnSO ₄ solution was added. This was washed with water, suction filtered, and dried to place zinc silicate on the surface of the core particles.

(Example 10)
The core particles were dispersed in an aqueous solution containing sodium polymetaphosphate, and adjusted to pH 8.0 by adding an aqueous calcium nitrate solution. This was washed with water, suction filtered, and dried to place calcium polyphosphate on the surface of the core particles.

Further, as shown in Table 1 below, phosphors of Examples 11 to 28 were obtained in the same manner as in Example 1 except that the composition of the core particles was changed. The composition of the core particles was adjusted by changing the weights of Eu ₂ O ₃ powder, CaCO ₃ powder, SrCO ₃ powder, and BaCO ₃ powder as raw material powder.

All of the phosphors of Examples 2 to 24 were excellent in moisture-proofing ability as A.

Also, except for changing the amount of of NH ₄ Cl as a crystal growth agent 0.5 wt%, to prepare core particles in the same manner as in Example 1, it was used as the fluorescent material of Comparative Example 2. The emission spectrum of the phosphor of Comparative Example 2 is shown in FIG. The first wavelength is 550 nm, and the second wavelength exists in the vicinity of 470 nm as shown in the figure. Due to the second wavelength, the spectral intensity ratio (Ia / Ib) increases as will be described later. Further, the composition of the core particles was changed as shown in Table 2 below, and TEOS was disposed on the surface thereof to obtain the phosphor of Comparative Example 3. The composition of the core particles was adjusted by changing the weights of Eu ₂ O ₃ powder, SrCO ₃ powder, and BaCO ₃ powder as raw material powder. The phosphor of Comparative Example 3 showed a large second wavelength, and Ia / Ib = 0.3.
The composition of the phosphor of the comparative example is summarized in Table 2 below together with moisture resistance.

  When the surface material is not present (Comparative Examples 1, 2, 7 to 12), when the value of y is small (Comparative Example 3), when the value of x is small (Comparative Example 4), the value of x is large and y When the value is small (Comparative Example 5) and when the value of y is large (Comparative Example 6), it is shown that the moisture resistance is inferior.

  Further, in the same manner as in Example 1 except that the phosphors of Examples 2 to 24 were used, light emitting devices of Examples 2 to 28 were fabricated in combination with an excitation light source having an excitation wavelength of 395 nm. Further, light emitting devices of Examples 29, 30, 31, 32, and 33 were produced in the same manner as in Example 1 except that the wavelength of the excitation light source was changed to 410 nm, 360 nm, 470 nm, 480 nm, and 405 nm.

The band wavelength, spectral intensity ratio, and light emitting device output of the light emitting device of the example are summarized in Table 3 below.

  As shown in Table 3, all the light emitting devices according to the embodiments of the present invention have a spectral intensity ratio (Ia / Ib) of 0.1 or less, and a sufficient output is obtained.

  The light emitting devices of Comparative Examples 2 to 7 were fabricated in combination with an excitation light source having an excitation wavelength of 395 nm, as in Comparative Example 1, except that the phosphors of Comparative Examples 2 to 7 were used. Further, light emitting devices of Comparative Examples 8, 9, 10, 11, and 12 were produced in the same manner as Comparative Example 1 except that the wavelength of the excitation light source was changed to 410 nm, 360 nm, 470 nm, 480 nm, and 405 nm. Aggregation occurred in the phosphor of Comparative Example 2 when dispersed in the silicone resin.

The band wavelength, spectral intensity ratio, and light emitting device output of the light emitting device of the comparative example are summarized in Table 4 below.

  In the light emitting device of Comparative Example 2, noticeable light emission unevenness was observed. This is presumably due to the aggregation of the phosphors.

  From the results of Table 4, it can be seen that when the spectral intensity ratio (Ia / Ib) is 0.3 (Comparative Examples 2 and 3), the output is extremely reduced. The comparison of the output is performed for the same excitation light source as in Example 29 and Comparative Example 8, for example. In any of the excitation light sources, it is clearly shown that the light emitting device of the example using the phosphor having high moisture proof power has a larger output than that of the comparative example.

The emission spectrum figure of the conventional europium activated silicate fluorescent substance. The emission spectrum figure of the europium activated silicate fluorescent substance concerning one Embodiment of this invention. Schematic showing the structure of the light-emitting device concerning one Embodiment of this invention. The emission spectrum figure of the europium activated silicate fluorescent substance of the comparative example 2.

Explanation of symbols

200 ... Resin stem; 201 ... Lead; 202 ... Lead; 203 ... Resin portion 204 ... Reflecting surface; 205 ... Recessed portion; 206 ... Light emitting chip 207 ... Bonding wire; 208 ... Bonding wire; 209 ... Phosphor layer 210 ... Phosphor; ... resin layer.

Claims (2)

A light-emitting element that emits light having a wavelength of 410 nm, 360 nm, 470 nm, or 405 nm;
A phosphor layer disposed on the light-emitting element and containing a phosphor;
The phosphor is disposed on the surface of the core particle composed of an alkaline earth metal silicate phosphor having a composition represented by the following general formula (1), and is a silicone resin, epoxy resin, fluororesin, tetraethoxy A surface layer material made of at least one selected from silane, silica, zinc silicate, aluminum silicate, calcium polyphosphate, silicone oil, and silicone grease, and excited by light having a wavelength of 410 nm, 360 nm, 470 nm, or 405 nm The light emission device has a single emission peak in the wavelength range of 540 nm to 600 nm.
(M _1-x Eu _x ) ₂ Si _y O _{2y + 2} (1)
(In the general formula (1), M is at least one alkaline earth metal element selected from the group consisting of Ca, Sr and Ba, x is 0.001 or more and 0.1 or less, and y is 0.00. 9 or more and 1.1 or less.) In the emission spectrum when excited with light having a wavelength of 410 nm, 360 nm, 470 nm, or 405 nm, the phosphor has a spectral intensity (Ib) at the first wavelength (λ _max nm) and a second wavelength (λmax-80 nm). 2) The ratio (Ia / Ib) to the spectral intensity (Ia) in (1) is 0.1 or less.

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